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CENTRAL FLORIDA EXPERIMENT STATION
S--- -------- Sanford, Florida
Mimeo Report CFES 67-1 March 23, 1967
APR 18 1967
SOYBEAN PRODUCTION ON ORGANIC SOILS OF CENTRAL FLORIDA
...1 ,' "-:W T. Scudder, Associate Horticulturist
Soybean production on Central Florida organic soils has been limited to only
a few hundred acres each year. Potentially, however, several thousand acres
could be grown annually. The land is used intensively throughout the winter and
spring for truck crops, but much of it is idle during the summer and fall. A
soybean crop occupying the land from mid-June until mid-November fits conveniently
into an annual rotation with vegetables. Maintenance of a soybean crop costs less
than clean fallow for summer weed control. Also, the weather during October and
November is normally dry, favorable for curing the crop in the field and permit-
ting the use of heavy combine equipment even on these soft peat soils. The
refuse from a soybean crop after combining is easily incorporated into the soil.
Disking will prepare a good seedbed for a winter vegetable crop.
Fertilization and Lime: Although the natural supply of phosphorus, potassi-
um, magnesium, and most of the essential micro-nutrients in the organic soils of
Central and South Florida is low, tests have shown that the residual fertilizer
from previous vegetable crops is ample for soybeans. The natural nitrogen con-
tent of these soils is very high, especially during the summer when soybeans are
grown. In their virgin state, these peat and muck soils range in pH from 3.5 to
6.5. However, for vegetable crops, most of the fields have been limed to bring
the pH up to at least 5.5. For soybean production, the more acid fields with
a pH of 5.7 or below should be avoided or limed sufficiently to correct the
acidity before planting.
Varieties:- Lee has produced better average yields than other available
varieties and is the only variety now recommended for the organic soils.
Average Yield in Bushels per Acre of Three Leading Soybean
Organic Soil at Zellwood, Florida
Varieties Grown on
1961 1962 1963 1964 4-Yr. Ave
Comm. Experi- Comm. Experi- Experi- Experi- Experi-
Variety Field mental Field mental mental mental mental
Lee 39 35 45 35 30 24 31.3
CNS-4 29 29 -- 23 27 22 24.7
Jackson 31 29 -- 22 16 18 23.0
Lee has good agronomic and disease resistance characters; however, plants of
this variety are sometimes shorter than the height required for maximum yields,
especially when plantings are made in July. Variety trials have identified ex-
perimental strains that are equal to Lee in most agronomic and disease resistance
qualities, are about 6 inches taller, and have averaged approximately 20 percent
higher yields over a 4 year period. One of these strains could be made available
if production increases enough to justify its release as a new variety. The best
varieties for the mineral soils of Central Florida usually are poorly adapted and
have not given satisfactory performance on the organic soils.
Planting: Plantings of Lee made between June 20 and July 10 have produced
good plant development and satisfactory yields. June plantings have given better
plant height and generally are superior to those made in July. A planting date
earlier than June 15 usually is impractical because of the spring vegetable
Seedbed preparation for soybeans is similar to that for vegetable crops.
The beans may be planted with corn planters using plates that drop 8 to 10 seeds
per foot of row. When average size seed are planted at this rate in rows 34 to
36 inches apart, 2/3 to 3/4 bushels per acre are required. Higher seeding rates
have not produced greater yields.
Planting seed should be inoculated with nitrogen-fixing bacteria unless
these bacteria are known to be present in the soil. Fields that have grown well-
nodulated soybeans require no further inoculation for many years. Also, on these
organic soils, wind may bring about the inoculation of adjacent fields by move-
ment of soil particles containing the bacteria. A grower can determine if he
needs to inoculate by collecting samples of soil from his fields, taking care to
prevent contamination, planting soybeans in the soil in pots, and checking after
2 to 3 weeks to see if nodules are produced. If inoculation is required, it is
important that the seed be planted within a few hours after treating them with
freshly cultured inoculant.
Good stands are difficult to obtain on moist organic soils because condi-
tions are very favorable for seed-rotting and damping-off organisms. Only high
quality seed should be used and it should be treated before planting with
chloranil (Spergon) or thiram (Arasan or Thylate). When inoculation with nitro-
gen-fixing bacteria is also needed, thiram is preferred since it is more compati-
ble with the inoculant than chloranil.
Weed Control: Weed emergence and growth on organic soils during June and
July are extremely rapid. Mechanical cultivation alone has failed to give ade-
quate weed control. Where chemical herbicides have not been used, even after
several cultivations, it has been necessary to plow under some fields. Large
weeds at harvest time seriously interfere with combining and result in consider-
able yield losses.
Of the several herbicides registered for use on soybeans, two have been
superior and have given consistently good weed control on Florida organic soils.
These are CDAA (Randox) and CDEC (Vegadex) applied immediately after planting
pre-emergence to the soybeans and weeds. A mixture of these two chemicals, using
3 pounds per acre of the active ingredient of each, is recommended for most
applications. Where annual grasses are the major problem, CDAA is preferred and
may be increased to 5 pounds per acre. CDEC is more effective on broadleaf weeds
and may be used at a maximum of 4 pounds per acre where these species predominate.:
In all mixtures, the total amount of both chemicals should not exceed 6 pounds
When applied at the proper time within 2 days of planting, both liquid and
granular herbicide formulations perform equally well. Broadcast applications
usually eliminate one or two early season cultivations, but are not preferred
because of the high cost. Instead, placement of the herbicide in bands 6 to 10
inches wide is recommended to control weed growth in the row, followed by culti-
vation to eliminate the weeds between the rows. Generally, the most satisfac-
tory results are obtained when the herbicide application accompanies planting.
Planter-attached sprayers or granular applicators are preferred, not only to
insure proper timing of the application, but also to keep the narrow band center-
ed over the row.
Insect Control: On organic soils, armyworms and stinkbugs are almost always
present in concentrations large enough to ruin a soybean crop. Armyworms usually
cause severe defoliation and loss of stand during the first few weeks after plant-
ing. The crop is never completely safe from armyworms, but late season attacks
are seldom serious. Armyworm damage is obvious but severe stinkbug damage may
go unnoticed by an inexperienced observer. Sinkbugs puncture and feed on young
pods causing excessive pod dropping and seed damage. In some cases, they have
reduced grain yields and quality below levels that would pay for combining in
fields where the grower thought insect control measures were not needed.
Armyworms have been satisfactorily controlled by two ground applications of
toxaphene sprayed at the rate of lY2 pounds of active ingredient per acre. The
use of toxaphene is not permitted late in the season or where the plants are to
be used for forage. Armyworms can be controlled without risking the possibility
of toxaphene residues by spraying with either carbaryl (Sevin) at Y1 pounds per
acre or TDE at 1 pound per acre of the active ingredients. With any of these
insecticides, two applications are required, the first as soon as the larvae
hatch, usually about one week after the soybeans emerge, and the second 10 to 14
To control stinkbugs, two applications of methyl parathion, each at 1/2
pound of active ingredient per acre, are required. The first treatment is made
as soon as stinkbugs are found in the field. This is usually around August 1.
The second application should follow 10 days later to kill newly hatched nymphs
and adults which escaped the first treatment and others which fly into the field.
Usually no further treatments are needed, though occasionally more applications
for one or both insect pests are found necessary. The timing of insecticide
applications and proper spray coverage are very important. Poorly adjusted
nozzles or a two-day delay after insects of either species appear may result in
a yield loss of several bushels per acre. Normally the soybean plants are large
and the space between the rows is filled by early August. Unless ground spray
equipment is available which will lift and part the vines without serious damage,
the methyl parathion should be applied by airplane. These control measures for
armyworms and stinkbugs also have been effective in controlling other insects
Mature and nearly mature armyworms and stinkbugs are commonly present on
the grass, weeds, and old crops of adjacent fields, headlands, fencerows, and
ditchbanks. Thorough border area sanitation at planting time to control these
hard-to-kill insects and keep them from moving into the soybean field is
essential. Where this is not practiced, even with adequate control of young
insects within the field, a band of soybeans 6 to 8 rows wide at the margins is
usually lost. Effective control of both these insects and the weeds and grass
around the fields may be obtained by wetting the foliage with a sodium arsenite
spray, using 3 gallons of the concentrate per 100 gallons of water.
Occasionally, a soybean field may contain large numbers of well developed
armyworms which had been feeding on crops and weeds in the field before it was
prepared for planting. These worms may survive for several days in hot soil and,
being very hungry,will quickly devour young emerging soybean plants. Where such
worms are present, the use of a toxaphene, Kepone, or other good armyworm bait is
recommended for use at planting time.
Harvesting and Drying Beans: The stems and pods normally are sufficiently
dry for combining soon after the leaves drop in late October or early November.
The crop should be harvested as soon as possible to prevent development of micro-
organisms in the beans and pods, to reduce yield loss from shattering, and to
avoid mechanical harvesting difficulties. Heavy dews, normal for these low-lying
organic soil areas, and rains, usually starting by early December, encourage pod
diseases and reduce seed quality. Also succulent weeds which seriously interfere
with combine operations develop rapidly in soybean fields after the plants
Preferably, the crop should be marketed immediately after harvest. When
the moisture in the beans is above 14 percent, there is danger from heating and
spoilage if an attempt is made to hold them over 4 or 5 days. Drying facilities
are available locally if it is found desirable to store them longer.
Marketing: U. S. production of soybeans during recent years has increased
continuously, but the national and worldwide market has been adequate to maintain
a favorable situation for growers. Efficient marketing locally, however, is
dependent upon adequate production volume and the presence of buyers in the area.
With limited acreage, growers face high marketing costs, especially for trans-
portation of the beans to buying stations or processing plants. A local buyer,
equipped with grading and drying facilities, can hold and pool small lots of
beans for large truck and carlot shipment. With local grading and drying,
quality is maintained and the price to the grower can be determined at the